1886.] ON A BRACHIOPOD OF THK GENUS ATRETIA. 181 



fact that the modification of the posterior air-sacs in Plafalea was 

 carried out on both sides of the body perhaps shows it to be a 

 characteristic of the bird. 



Alimentary Canal. — The caeca oiChauna chavaria appear to differ 

 slightly from those of Okauna derbiana, the most noticeable diiFerence 

 being that they are not symmetrical in the former species ; the right 

 caecum is slightly longer than the left, and is of a uniform conical 

 shape, tapering sliglitly to the free extremity ; it measured 3| inches 

 from the tip to the junction with the ilium ; the left caecum measured 

 as nearly as possible 3 inches. The left caecum also differs in its shape, 

 as may be seen by an inspection of the accompanying drawing 

 (p. 180); its proximal half is about equal in diameter to that of the 

 right caecum, but instead of tapering gradually it narrows abruptly 

 into the distal half, which is of about the thickness of the little 

 finger. 



In the liver the right lobe is larger than tlie left lobe, and, as in 

 the other species, there is a large gall-bladder the duct of which 

 opens into the duodenum below the hepatic duct ; the pancreatic 

 duct is the most anterior of the three. 



Trachea. — The extrinsic muscl?s of the syrinx are somewhat 

 differently disposed from those of Chauna derbiana ; as in that 

 species, there are two pairs ; the most anterior spreads out in a fan-like 

 manner upon a tough membrane which connects the coracoid and 

 clavicle ; this muscle is therefore attached exactly as is its homologue 

 in Ch. derbiana. The posterior pair of muscles are, however, not 

 attached to the costal process of the sternum as in Ch. derbiana, but 

 terminate upon the aponeurosis of the lung just behind the exit of 

 the pulmonary vein. The syrinx itself does not appear to me to be 

 worth a special description or figure, as it agrees in every particular 

 with that of Ch. derbiana. 



2. On a Brachiopod of the Genus Atreiia, named in MS. 

 by the late Dr. T. Davidson. By Miss Agnes Crane. 

 (Communicated by Prof. W. H. Flower, LL.D., F.R.S.) 



[Received March 15, 1886.] 



In July last the late Dr. Thomas Davidson, F.R.S., received from 

 Mr. John Brazier, of Sydney, a gift of an interesting series of 

 Brachiopoda dredged by him in the waters of Port Stephens and 

 Port Jackson, New South Wales. When, in January 188G, it became 

 my duty to select the remaining specimens from the Davidson 

 collection necessary for the ilkistration of Parts 2 and 3 of Dr. 

 Davidson's forthcoming Monograph on Recent Brachiopoda, these 

 Austrahan specimens were not found incorporated with his collection 

 of living species. Possibly it was Dr. Davidson's intention to describe 

 them in a separate paper. In February, when the collection of recent 

 and fossil Brachiopoda (which, in accordance with Dr. Davidson's 



